1. Field of the Invention
The present invention relates to a confocal microscope having a focal point detecting function and, more particularly, to a scanning confocal microscope for observing the surface of an object such as, especially, a semiconductor wafer, a photomask, and a semiconductor integrated device for a liquid crystal display.
2. Description of the Related Art
FIG. 9 is a drawing showing the construction of a conventional confocal microscope. In the figure, reference numeral 91 denotes a point light source, 92 a beam splitter, 93 an objective lens, 95 a stage on which an object is placed or to be placed, 96 a diaphragm for allowing the passage of only a part of light split by the beam splitter that converges on or in the vicinity of a focal point of the light so split, and 97 a light detector.
In operation, irradiated light from the point light source 91 passes through the beam splitter 92 and is focussed on the surface of the object 94 by the objective lens 93, and a part of light reflected from the surface of the object is split by the beam splitter 92 so as to pass through the diaphragm 96, and light that has passed through the diaphragm 96 is focussed on a detecting portion of the light detector 97. The surface of the object 94 is observed by moving the point light source 91 so as to scan the entire surface of the object 94 and repeating the aforementioned procedure.
In order for light from the point light source 91 to be focussed on the object 94, the stage 95 on which the object 94 is placed needs to be moved by hand so as to adjust the position of the object 94.
In the above prior art, if there are irregularities on the surface of the stage 95 on which the object 94 is placed, or if there are irregularities on the surface of the object, or if the surface of the stage or object is warped, every time such is found, the position of the stage 95 has to be manually adjusted, this making the operation of a confocal microscope complicated and troublesome.